Did you know that Nathaniel Hawthrone wrote a biography of Franklin Pierce? This was part of his campaign! Hawthrone and Pierce actually went to school together and hence he was supporting the presidential campaign the best way he could - with the pen.
Here's an excerpt from Chapter 5, his time in Mexico:
resisted the American advance; while the artillery of the intrenched camp played upon our troops, and shattered the very rocks over which they were to pass.
General Pierce's immediate command had never before been under such a fire of artillery. The enemy's range was a little too high, or the havoc in our ranks must have been dreadful. In the midst of this fire, General Pierce, being the only officer mounted in the brigade, leaped his horse upon an abrupt eminence, and addressed the colonels and captains of the regiments, as they passed, in a few stirring words--reminding them of the honor of their country, of the victory their steady valor would contribute to achieve. Pressing forward to the head of the column, he had nearly reached the practicable ground that lay beyond, when his horse slipped among the rocks, thrust his foot into a crevice, and fell, breaking his own leg, and crushing his rider heavily beneath him.
Pierce's mounted orderly soon came to his assistance. The general was stunned, and almost insensible. When partially recovered, he found himself suffering from severe bruises, and especially from a sprain of the left knee, which was undermost when the horse came down. The orderly assisted him to reach the shelter of a projecting rock; and as they made their way thither, a shell fell close beside them, and exploded, covering them with earth. "That was a lucky miss," said Pierce calmly. Leaving him in such shelter as the rock afforded, the orderly went in search of aid, and was fortunate to meet with Dr. Ritchie, of Virginia, who was attached to Pierce's brigade, and was following in close proximity to the advancing column. The doctor administered to him as well as the circumstances would admit. Immediately on recovering his full consciousness, General Pierce had become anxious to rejoin his troops; and now, in opposition to Dr. Ritchie's advice and remonstrances, he determined to proceed to the front.
With pain and difficulty, and leaning on his orderly's arm, he reached the battery commanded by Captain McGruder, where he found the horse of Lieutenant Johnson, who had just before received a mortal wound. In compliance with his wishes, he was assisted into the saddle; and, in answer to a remark that he would be unable to keep his seat, "Then," said the general, "you must tie me on." Whether this precaution was actually taken is a point on which authorities differ; but at, all events, with injuries so severe as would have sent almost any other man to the hospital, he rode forward into the battle.
The contest was kept up until nightfall, without forcing Valencia's intrenchment. General Pierce remained in the saddle until eleven o'clock at night. Finding himself, at nine o'clock, the senior officer in the field, he, in that capacity, withdrew the troops from their advanced position, and concentrated them. at the point where they were to pass the night. At eleven, beneath a torrent of rain, destitute of a tent or other protection, and without food or refreshment, he lay down on an ammunition wagon, but was prevented by the pain of his injuries, especially that of his wounded knee, from finding any repose. At one o'clock came orders from General Scott to put the brigade into a new position, in front of the enemy's works, preparatory to taking part in the contemplated operations of the next morning. During the night, the troops appointed for that service, under Riley, Shields, Smith, and Cadwallader, had occupied the villages and roads between Valencia's position and the city; so that, with daylight, the commanding general's scheme of the battle was ready to be carried out, as it had originally existed in his mind.
At daylight, accordingly, Valencia's entrenched camp was assaulted. General Pierce was soon in the saddle, at the head of his brigade, which retained its position in front, thus serving to attract the enemy's attention, and divert him from the true point of attack. The camp was stormed in the rear by the American troops, led on by Riley, Cadwallader, and Dimmick; and in the short space of seventeen minutes it had fallen into the hands of the assailants, together with a multitude of prisoners. The remnant of the routed enemy fled towards Churubusco. As Pierce led his brigade in pursuit, crossing the battle field, and passing through the works that had just been stormed, he found the road and adjacent fields every where strewn with the dead and dying. The pursuit was continued until one o'clock, when the foremost of the Americans arrived in front of the strong Mexican positions at Churubusco and San Antonio, where Santa Anna's army had been compelled to make a stand, and where the great conflict of the day commenced.
General Santa Anna entertained the design of withdrawing his forces towards the city. In order to intercept this movement, Pierce's brigade, with other troops, was ordered to pursue a route by which the enemy could be attacked in the rear. Colonel Noah E. Smith (a patriotic American, long resident in Mexico, whose local and topographical knowledge proved eminently serviceable) had offered to point out the road, and was sent to summon General Pierce to the presence of the commander-in-chief. When he met Pierce, near Coyacan, at the head of his brigade, the heavy fire of the batteries had commenced. "He was exceedingly thin," writes Colonel Smith, "worn down by the fatigue and pain of the day and night before, and then evidently suffering severely. Still, there was a glow in his eye, as the cannon boomed, that showed within him a spirit ready for the conflict." He rode up to General Scott, who was at this time sitting on horseback beneath a tree, near the church of Coyacan, issuing orders to different individuals of his staff. Our account of this interview is chiefly taken from the narrative of Colonel Smith, corroborated by other testimony.
The commander-in-chief had already heard of the accident that befell Pierce the day before; and as the latter approached, General Scott could not but notice the marks of pain and physical exhaustion, against which only the sturdiest constancy of will could have enabled him to bear up. "Pierce, my dear fellow," said he,--and that epithet of familiar kindness and friendship, upon the battle field, was the highest of military commendation from such a man,--"you are badly injured; you are not fit to be in your saddle." "Yes, general, I am," replied Pierce, "in a case like this." "You cannot touch your foot to the stirrup," said Scott. "One of them I can," answered Pierce. The general looked again at Pierce's almost disabled figure, and seemed on the point of taking his irrevocable resolution. "You are rash, General Pierce," said he; "we shall lose you, and we cannot spare you. It is my duty to order you back to St. Augustine." "For God's sake, general," exclaimed Pierce, "don't say that! This is the last great battle, and I must lead my brigade!" The commander-in-chief made no further remonstrance, but gave the order for Pierce to advance with his brigade.
The way lay through thick standing corn, and over marshy ground intersected with ditches, which were filled, or partially so, with water. Over some of the narrower of these Pierce leaped his horse. When the brigade had advanced about a mile, however, it found itself impeded by a ditch ten or twelve feet wide, and six or eight feet deep. It being impossible to leap it, General Pierce was lifted from his saddle, and, in some incomprehensible way, hurt as he was, contrived to wade or scramble across this obstacle, leaving his horse on the hither side. The troops were now under fire. In the excitement of the battle, he forgot his injury, and hurried forward, leading the brigade, a distance of two or three hundred yards. But the exhaustion of his frame, and particularly the anguish of his knee,--made more intolerable by such free use of it,--was greater than any strength of nerve, or any degree of mental energy, could struggle against. He fell, faint and almost insensible, within full range of the enemy's fire. It was proposed to bear him off the field; but, as some of his soldiers approached to lift him, be became aware of their purpose, and was partially revived by his determination to resist it. "No," said he, with all the strength he had left, "don't carry me off! Let me lie here!" And there he lay, under the tremendous fire of Churubusco, until the enemy, in total rout, was driven from the field.